Class B scavenger receptors are members of the CD36 protein family that mediate lipid uptake and mobilisation. Bez is a scavenger receptor in Drosophila with its role yet to be characterised. Here, Margret Bülow and colleagues uncover a role of Bez in mobilising lipids from Drosophila adipocytes into the ovary for oocyte maturation. First, looking at the structure and expression pattern of Bez, the authors find that Bez contains a conversed lipid-binding residue homologous to CD36 and is expressed at the plasma membrane of adipocytes. Then, the authors observe that, in bez mutants, egg chambers in ovaries cannot mature properly and lipids from adipocytes cannot be mobilised upon starvation. Furthermore, the authors demonstrate that Bez interacts with Lipophorin, a lipoprotein that transports lipids between organs, at the plasma membrane of adipocytes. Lipidomics analysis of bez mutants shows that lipids accumulate in fat body tissue, while lipid content is reduced in Lipophorins. Finally, by tracing an alkyne-labelled fatty acid, the authors find that, compared with the control, bez mutants are unable to transfer lipids from fat body tissue to Lipophorin. Overall, the findings suggest that Bez is required for lipid export from adipocytes and regulates the distribution of lipids to ovaries via lipoproteins.
